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+// Copyright (c) 2011 The Chromium Authors. All rights reserved. |
+// Use of this source code is governed by a BSD-style license that can be |
+// found in the LICENSE file. |
+ |
+// Derived from google3/util/gtl/stl_util.h |
+ |
+#ifndef BASE_STL_UTIL_H_ |
+#define BASE_STL_UTIL_H_ |
+#pragma once |
+ |
+#include <assert.h> |
+#include <string.h> // for memcpy |
joth
2011/07/20 11:38:48
we don't actually call memcpy anymore.
Denis Lagno
2011/07/20 12:01:13
thanks for noticing.
And BTW we do not call asser
|
+ |
+#include <string> |
+#include <vector> |
+ |
+// Clear internal memory of an STL object. |
+// STL clear()/reserve(0) does not always free internal memory allocated |
+// This function uses swap/destructor to ensure the internal memory is freed. |
+template<class T> void STLClearObject(T* obj) { |
+ T tmp; |
+ tmp.swap(*obj); |
+ // Sometimes "T tmp" allocates objects with memory (arena implementation?). |
+ // Hence using additional reserve(0) even if it doesn't always work. |
+ obj->reserve(0); |
+} |
+ |
+// STLDeleteContainerPointers() |
+// For a range within a container of pointers, calls delete |
+// (non-array version) on these pointers. |
+// NOTE: for these three functions, we could just implement a DeleteObject |
+// functor and then call for_each() on the range and functor, but this |
+// requires us to pull in all of algorithm.h, which seems expensive. |
+// For hash_[multi]set, it is important that this deletes behind the iterator |
+// because the hash_set may call the hash function on the iterator when it is |
+// advanced, which could result in the hash function trying to deference a |
+// stale pointer. |
+template <class ForwardIterator> |
+void STLDeleteContainerPointers(ForwardIterator begin, ForwardIterator end) { |
+ while (begin != end) { |
+ ForwardIterator temp = begin; |
+ ++begin; |
+ delete *temp; |
+ } |
+} |
+ |
+// STLDeleteContainerPairPointers() |
+// For a range within a container of pairs, calls delete |
+// (non-array version) on BOTH items in the pairs. |
+// NOTE: Like STLDeleteContainerPointers, it is important that this deletes |
+// behind the iterator because if both the key and value are deleted, the |
+// container may call the hash function on the iterator when it is advanced, |
+// which could result in the hash function trying to dereference a stale |
+// pointer. |
+template <class ForwardIterator> |
+void STLDeleteContainerPairPointers(ForwardIterator begin, |
+ ForwardIterator end) { |
+ while (begin != end) { |
+ ForwardIterator temp = begin; |
+ ++begin; |
+ delete temp->first; |
+ delete temp->second; |
+ } |
+} |
+ |
+// STLDeleteContainerPairFirstPointers() |
+// For a range within a container of pairs, calls delete (non-array version) |
+// on the FIRST item in the pairs. |
+// NOTE: Like STLDeleteContainerPointers, deleting behind the iterator. |
+template <class ForwardIterator> |
+void STLDeleteContainerPairFirstPointers(ForwardIterator begin, |
+ ForwardIterator end) { |
+ while (begin != end) { |
+ ForwardIterator temp = begin; |
+ ++begin; |
+ delete temp->first; |
+ } |
+} |
+ |
+// STLDeleteContainerPairSecondPointers() |
+// For a range within a container of pairs, calls delete |
+// (non-array version) on the SECOND item in the pairs. |
+template <class ForwardIterator> |
+void STLDeleteContainerPairSecondPointers(ForwardIterator begin, |
+ ForwardIterator end) { |
+ while (begin != end) { |
+ delete begin->second; |
+ ++begin; |
+ } |
+} |
joth
2011/07/20 11:38:48
fwiw server now has this as
while (begin != end)
Denis Lagno
2011/07/20 12:01:13
yes, it looks better to sync with server.
|
+ |
+// To treat a possibly-empty vector as an array, use these functions. |
+// If you know the array will never be empty, you can use &*v.begin() |
+// directly, but that is undefined behaviour if v is empty. |
+ |
+template<typename T> |
+inline T* vector_as_array(std::vector<T>* v) { |
+# ifdef NDEBUG |
+ return &*v->begin(); |
joth
2011/07/20 11:38:48
this always seems to me to be a quite obscure non-
Denis Lagno
2011/07/20 12:54:36
agree, chromium (client) and server differs in tha
|
+# else |
+ return v->empty() ? NULL : &*v->begin(); |
+# endif |
+} |
+ |
+template<typename T> |
+inline const T* vector_as_array(const std::vector<T>* v) { |
+# ifdef NDEBUG |
+ return &*v->begin(); |
+# else |
+ return v->empty() ? NULL : &*v->begin(); |
+# endif |
+} |
+ |
+// Return a mutable char* pointing to a string's internal buffer, |
+// which may not be null-terminated. Writing through this pointer will |
+// modify the string. |
+// |
+// string_as_array(&str)[i] is valid for 0 <= i < str.size() until the |
+// next call to a string method that invalidates iterators. |
+// |
+// As of 2006-04, there is no standard-blessed way of getting a |
+// mutable reference to a string's internal buffer. However, issue 530 |
+// (http://www.open-std.org/JTC1/SC22/WG21/docs/lwg-active.html#530) |
+// proposes this as the method. According to Matt Austern, this should |
+// already work on all current implementations. |
joth
2011/07/20 11:38:48
FWIW, C++ 2008 does now clarify this:
21.3.1 basi
|
+inline char* string_as_array(std::string* str) { |
+ // DO NOT USE const_cast<char*>(str->data()) |
+ return str->empty() ? NULL : &*str->begin(); |
+} |
+ |
+// The following functions are useful for cleaning up STL containers |
+// whose elements point to allocated memory. |
+ |
+// STLDeleteElements() deletes all the elements in an STL container and clears |
+// the container. This function is suitable for use with a vector, set, |
+// hash_set, or any other STL container which defines sensible begin(), end(), |
+// and clear() methods. |
+// |
+// If container is NULL, this function is a no-op. |
+// |
+// As an alternative to calling STLDeleteElements() directly, consider |
+// STLElementDeleter (defined below), which ensures that your container's |
+// elements are deleted when the STLElementDeleter goes out of scope. |
+template <class T> |
+void STLDeleteElements(T *container) { |
+ if (!container) return; |
+ STLDeleteContainerPointers(container->begin(), container->end()); |
+ container->clear(); |
+} |
+ |
+// Given an STL container consisting of (key, value) pairs, STLDeleteValues |
+// deletes all the "value" components and clears the container. Does nothing |
+// in the case it's given a NULL pointer. |
+ |
+template <class T> |
+void STLDeleteValues(T *v) { |
+ if (!v) return; |
+ for (typename T::iterator i = v->begin(); i != v->end(); ++i) { |
+ delete i->second; |
+ } |
+ v->clear(); |
+} |
+ |
+ |
+// The following classes provide a convenient way to delete all elements or |
+// values from STL containers when they goes out of scope. This greatly |
+// simplifies code that creates temporary objects and has multiple return |
+// statements. Example: |
+// |
+// vector<MyProto *> tmp_proto; |
+// STLElementDeleter<vector<MyProto *> > d(&tmp_proto); |
+// if (...) return false; |
+// ... |
+// return success; |
+ |
+// Given a pointer to an STL container this class will delete all the element |
+// pointers when it goes out of scope. |
+ |
+template<class STLContainer> class STLElementDeleter { |
+ public: |
+ STLElementDeleter<STLContainer>(STLContainer *ptr) : container_ptr_(ptr) {} |
+ ~STLElementDeleter<STLContainer>() { STLDeleteElements(container_ptr_); } |
+ private: |
+ STLContainer *container_ptr_; |
+}; |
+ |
+// Given a pointer to an STL container this class will delete all the value |
+// pointers when it goes out of scope. |
+ |
+template<class STLContainer> class STLValueDeleter { |
+ public: |
+ STLValueDeleter<STLContainer>(STLContainer *ptr) : container_ptr_(ptr) {} |
+ ~STLValueDeleter<STLContainer>() { STLDeleteValues(container_ptr_); } |
+ private: |
+ STLContainer *container_ptr_; |
+}; |
+ |
+// Test to see if a set, map, hash_set or hash_map contains a particular key. |
+// Returns true if the key is in the collection. |
+template <typename Collection, typename Key> |
+bool ContainsKey(const Collection& collection, const Key& key) { |
+ return collection.find(key) != collection.end(); |
+} |
+ |
+#endif // BASE_STL_UTIL_H_ |